Higher Serum Free T4 Is Associated With Increased Risk of Mortality and Cerebrovascular Events in Elderly Men

Background It is unclear whether thyroid hormone levels are associated with the risk of mortality, cardiovascular disease (CVD) events, or cancer in men with normal TSH. Objectives We analyzed if serum free T4 (FT4) or TSH is associated with the risk of mortality, incident CVD events, or cancer in Swedish men. Methods Elderly men (n = 1801; mean age 75 years) in the Gothenburg and Malmö subcohorts of the prospective, population-based Osteoporotic Fractures in Men Study-Sweden study were followed for median 12.2 years regarding all-cause mortality [1207 (67%) died] and for median 5.1 years regarding incident CVD events (n = 338) and cancer (n = 249). The statistical analyses included Cox proportional hazards regression with adjustment for covariates including prevalent atrial fibrillation (AF). Results Serum FT4 (per SD increase) was associated with increased risk of mortality [men with normal TSH: fully adjusted hazard ratio (HR) 1.23, 95% confidence interval (CI): 1.11-1.35] and incident CVD events (HR 1.25, 95% CI: 1.05-1.48) but not with the risk of cancer. The association between FT4 and CVD events was mainly due to increased risk of cerebrovascular (CBV) events (HR 1.56, 95% CI: 1.24-1.96). Finally, TSH was not associated with the risk of mortality, CVD events, or cancer. Conclusion FT4, but not TSH, is a predictor of mortality risk in elderly men. The association between FT4 and elevated risk of CVD events was mostly due to increased risk of CBV events, which remained significant also after adjustment for prevalent AF.